Light petroleum fractions from refinery and petrochemical operations constitute a potentially valuable raw material source for the production of styrene and other commercially important aromatic compounds.
Processes for the conversion of light paraffins to aromatic hydrocarbons at some stage usually involve naphthenic compounds. A well-known reaction is the dehydrocyclization of C.sub.6 and higher paraffins to aromatic derivatives containing the same number or less carbon atoms than the feed material. Under the severe processing conditions typical of petroleum refinery reforming operations, dehydrogenation and dehydrocyclization conversions of light petroleum mixtures are accompanied by competing isomerization, cracking and coking reaction mechanisms. Efforts to develop economical processes for selective production of naphthene and aromatic products from readily available acyclic hydrocarbon raw materials have encountered many difficulties. An extensive technology has been developed which has endeavored to solve the most serious of the technical problems, and provide valuable naphthene and aromatic products with greater selectivity and efficiency from C.sub.6 and higher acyclic hydrocarbons.
U.S. Pat. No. 2,212,026 describes the conversion of n-octane to p-xylene and ethylbenzene at 200.degree. C.-400.degree. C. in the presence of a catalyst mixture of alumina and nickel metal. In a similar process, U.S. Pat. No. 2,217,011 describes the conversion of 1-octyne to o-xylene, and U.S. Pat. No. 2,217,012 discloses the conversion of 1,4-octadiene to o-xylene.
U.S. Pat. No. 2,328,755 describes a process which involves contacting n-octene with silica/alumina hydrogel at 710.degree. F. and atmospheric pressure to yield a mixture of paraffins, naphthenes and aromatic compounds.
U.S. Pat. No. 2,775,631 describes a process which involves the conversion of a normal olefin into an aromatic compound by contacting the olefin and carbon dioxide with a molybdenum oxide catalyst at a temperature of 750.degree.-1100.degree. F.
U.S. Pat. No. 3,202,725 describes a process for producing xylene from C.sub.8 acyclic hydrocarbons such as diisobutylene employing a catalysts consisting of chromium oxide on eta alumina.
U.S. Pat. No. 3,308,193 describes a process which involves oxidative dehydrogenation of hydrocarbons to form aromatic compounds. 2-Ethylhexene-1 was contacted with a Fe.sub.3 O.sub.4 /CaO catalyst at 500.degree. C. in the presence of oxygen and steam to yield toluene, ethylbenzene, p-xylene, o-xylene and styrene.
U.S. Pat. No. 3,686,341 describes a process for the aromatization of olefinic hydrocarbons which comprises contacting C.sub.6 -C.sub.12 olefinic hydrocarbons at 300.degree. C.-800.degree. C. and 15-150 psi with a catalyst consisting of a chrysotile and a transition metal component selected from Group VIB and Group VIII metals.
U.S. Pat. No. 3,758,600 describes a Group VIB metal oxide deposited on a support comprising a mixture of titania and alumina for use as a catalyst to promote the conversion of paraffins, olefins, cycloparaffins and cycloolefins to aromatics at a temperature of 400.degree. F.-1200.degree. F.
U.S. Pat. No. 3,903,185 describes a method of manufacturing ethylbenzene by catalytic aromatization of the C.sub.8 -cycloolefins obtained in the dimerization of unsaturated C.sub.4 -hydrocarbons. The catalyst is a metal and/or metal oxide of sub-groups VI, VII and VIII including the platinum metals.
U.S. Pat. No. 4,056,575 describes a process for the production of aromatic hydrocarbons which involves subjecting an unsaturated hydrocarbon containing at least 6 carbon atoms to aromatization in the presence of a catalyst consisting essentially of gallium deposited on a support.
Other patents relating to the conversion of acyclic hydrocarbons to naphthenes and aromatic compounds include U.S. Pat. Nos. 2,124,584; 2,172,535; 2,271,751; 2,316,271; 2,320,147; 2,336,783; 2,344,318; 2,386,957; 2,394,170; 2,423,176; 2,441,297; 2,508,014; 2,598,642; 2,857,442; 2,992,283; 3,013,089; 3,251,900; 3,325,552; 3,480,684; 3,501,542; 3,548,021; 3,579,598; 3,670,044; 3,719,721; 3,758,600; 3,775,502; 3,981,794; 4,104,320; and the like.
Accordingly, it is an object of this invention to provide an improved process for converting light acyclic hydrocarbons into cyclic hydrocarbons.
It is another object of this invention to provide an improved process for converting n-octenes into naphthenes and aromatic hydrocarbons.
It is a further object of this invention to provide an improved two-step process for converting n-octenes into styrene.
Other objects and advantages shall become apparent from the following description and examples.